Railway signaling for intersecting tracks



July 1, 1958 R. R. KEMMERER RAILWAY SIGNALING FOR INTERSECTING TRACKS 4 Sheets-Sheet 2 Filed Dec.

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RAILWAY SIGNALING FOR INTERSECTING TRACKS Filed Dec. 23, 1955 4 Sheets-Sheet 3 when y 1958 R. R.'KEMMERER RAILWAY SIGNALING FOR INTERSECTING TRACKS 4 Sheets-Sheet 4 Filed Dec.

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m Mi w w Z 2 C & m2 Q m n fig m w m m Help/2 bfiiwzzzzenen nited States RAEWAY SIGNALING FOR INTERSECTIN G TRACKS Appiication December 23, 1955, Serial No. 554,953

Claims. (Cl. 246-161) My invention relates to railway signaling, and particularly to the automatic control of signals for traflic movements along intersecting tracks.

Certain aspects of the matter disclosed and claimed in this application are disclosed but not claimed in my copending application Serial No. 300,563, filed July 23, 1952, and now Patent No. 2,760,054 for Apparatus for Controlling Highway Crossing Signals.

in some forms of previous interlocking circuits for intersecting tracks the signal for a particular direction of travel or route is cleared and is subsequently maintained cleared for that direction of travel by a directional stick relay which is energized upon approach of a train, and held energized until the train has progressed for a predetermined distance past the crossing. The directional stick relay is maintained energized by the successive deenergization of the track relays for that route as the train progresses through the route. It has been found in some cases, however, that when a second train enters the approach section of a conflicting route after a first train has established another route, if a loss of shunt occurs in the established route, the directional stick relay for that route may become deenergized and thus enable the signals for the conflicting route to be cleared. This is undesirable in the interest of safety.

It is, therefore, an object of my invention to provide an automatic signaling system for intersecting tracks including means for preventing improper clearing of signals due to momentary loss of shunt of any part of an established route.

Another object of my invention is to provide directional stick relay control for an interlocking or intersec tion of conflicting routes that is not affected by momentary shunt losses of a train passing through the interlockmg.

Another object of my invention is to provide an interlocking approach stick relay control capable of providing the advantages of the protection of a time delay in the reenergization of the approach stick relay Without the disadvantages of train delays due to long time periods.

Other objects and purposes and characteristic features of my invention will be in part obvious from the accompanying drawings and in part pointed out as the description of my invention progresses.

In practicing my invention I provide a signal control system for intersecting tracks which is free from malfunction due to momentary losses of track shunt of an established route. The protection is obtained through momentary loss of track shunt protection being given to approach stick relays for controlling the entering signals and routing relay as well as providing the directional stick relay with additional stick circuit paths for preventing the directional stick relay from being deenergized due to a momentary loss of shunt during approach or recession of any vehicle. My novel circuit control of the interlocking circuits allows the elimination of parallel circuits for selective quick reenergization or the timingout of the approach stick relays by extended. time period atent thermal time element relays since the use of long time periods becomes unnecessary; therefore, allowing a shorter time period to be used under all controls.

I shall now describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Figs. 1a to ld, inclusive, are diagrammatic views which, when placed side to side with Fig. la on the left, show one form of apparatus embodying my invention applied to an automatic interlocking system involving a crossing of two single track railroad lines.

Similar reference characters refer to similar parts in each of the views.

Referring to the drawings, intersecting railway tracks, designated by the reference characters X and Z, are divided into sections by the usual insulated joints 5. Track X is divided into sections DlT, 1T, AIT and DZT, and track Z is divided into sections D31", 3T, A31 and D41. A track battery 6 is connected across the rails adjacent one end of each section and a track relay, designated by the reference character R with a prefix comprising the reference character for the associated track section, is connected across the rails adjacent to the opposite end of each section. Track sections DlT, D3T, D4 1, and DZT will be referred to as approach sections and sections 1T, ET, and ART and AST will be referred to as crossing track sections.

Signals designated by the reference characters 1 and 2 are located adjacent the ends of the track sections IT and A11, respectively, for governing trafiic movements in opposite directions on track X across the intersection of the two tracks. Signals designated by the reference characters 3 and 5- are located adjacent the ends of the track sections ST and ASST respectively for governing trafiic movements in opposite directions on track Z across the intersection of the two tracks. As here shown each of the signals is of a semaphore type and has a proceed and stop position, but may be of any other suitable type.

For each of the signals 1', 2, 3, and 4 there is shown a signal operating mechanism designated as 18, 2G, 3G, and 4G, respectively.

Each of the signal mechanisms 1G, 2G, 3G, and 4G is provided with a signal repeater relay each designated by the reference character RGPR preceded by the reference character for its particular signal. The circuit for controlling these repeater relays is not shown but each is designated as being energized when its particular signal mechanism is positioned to control the signal to display a red or restrictive aspect.

Time element devices l-2TE and (shown in Fig. lb) are manually controllable and may be of the well-known clockwork release type. Each of these devices has contacts such as contacts a, c, d, and 1 that are closed in only the normal or run-down position as shown in the drawing. Other contacts, such as contacts b and e, of the time element devices, however, may be of the type that are closed during the time that the clockwork mechanism is returning to the normal position after having been wound up to the reverse position. These contacts, for example, may become closed 30 seconds before the device reaches the normal position and may be opened again 10 seconds before the device reaches the normal position. A further explanation of the time element devices 12TE and 3 3TE is considered unnecessary, since the specific mechanism of these devices does not form a part of my invention. A further explanation of the operation, however, can be found in the E. M. Allen Patent No. 2,289,857 issued July 14, 194-2.

Fig. 1c shows a route selecting relay RR controlled over a front contact of a route locking relay RLR which is controlled over polar contact a of the route selecting relay RR. The circuits shown also include a polar contact b of the route selecting relay RR in both the normal and reverse positions for energizing route indication lamps l-ZE and 3-4E, respectively.

Figures lb and 1c show directional stick relays 18R, 25R, 33R and 48R, each of which becomes energized when a train enters its corresponding crossing section with the mechanism g of the corresponding signal in proceed position, and which is retained in the energized condition as a train recedes from the intersection. Each of the directional stick relays is maintained energized during passage of a train through the intersecting tracks over a track repeater relay I3TPSR which isprovided with loss of shunt protection to be explained hereinafter.

Figures 1a and 1a show pickup and stick circuits for approach stick relays lASR, ZASR, 3ASR, and 4ASR with the approach stick relays being controlled over a thermal time element relay and also provided with loss of shunt protection circuits to be explained hereinafter.

Having described in general the arrangement of various parts of the apparatus embodying my invention, I shall.

now describe in detail the operation of this form of apparatus.

As shown in the drawing all parts are in the normal condition; that is, each of the track sections is unoccupied, and hence the track relays are energized. The mechanism for each of the signals is deenergized, and the signals are all displaying stop indication. Under these conditions the relays lRGPR, ZRGPR, SRGPR, 4RGPR, RLR, 1ASR, ZASR, SASR, and 4ASR, are all energized. Relays RR, 13R, 28R, 38R, and 48R and the time element relays EATER, ZATER, SATER, EATER, and 13TER are deenergized, and the route indication lamps 1-2E and 3-4E are extinguished.

Relays RLR, 18R, 28R, 38R and 48R are provided with shunting resistors to slightly delay the dropping away of the contacts of these relays. The shunting resistors are provided to assure proper sequence of operation of the circuits controlled by these relays.

Relay RLR is energized by a circuit passing from one terminal B of a suitable source of power, not shown in the drawing, through front contact a of relay ZASR, conductor 1%, front contact b of relay lASR, conductors 16 and 57, polar contact a of the routing relay RR closed in its left hand position, the winding of RLR, conductor 39, and the front contact f of relay 13TPSR to terminal C of the source of power.

The relay l3TPSR is a track relay stick repeater relay for the crossing sections 1T, AlT, 3T, and A3T. The relay 13TPSR is shown maintained energized over a stick circuit passing from the source terminal B over front contact a of relay lTR, front contact a of relay 3TR, wire 31, front contact a of relay AlTR, front contact a of relay A3TR, wire 34, the winding of the time element thermal relay 1 3TER all connected in parallel with front contact b of the track relay lTR, front contact b of the track relay 3TR, wire 32, front contact b of the track relay AlTR, front contact b of the track relay A3'iR, wire 33 and the winding of the thermal relay repeater relay Ii-3TESR, both portions being connected together and through the front contact a of the relay 1-3TPSR and the winding of the relay 13TPSR to the C terminal of the source of power. The stick circuit just traced maintains the relay l3TPSR energized over its own front contact and over the windings of the relay 1-3TESR and the time element relay 13TER connected in parallel. The relay 13TPSR is capable of remaining energized on a current that is insufficient to energize the relay 13TESR and the time element relay 13TER to the extent necessary to cause these two relays to operate their contacts, and the parts are so proportioned that the relay 1-3TPSR is the only relay which will hold its contacts in the energized position under these conditions. The presence of a train in any of the crossing track sections 1T, AlT, ST, and A3T will cause the stick circuit for relay 1-3TPSR to be interrupted, whereupon the relay 13TPSR will close its back contact a. The closing of the back contact a of the relay 13TPSR prepares a pickup circuit for the relay 1-3TESR and the time element relay ]l--3TER. This pickup circuit for the time element relay 1-3TER and relay 13TESR, is controlled over a back contact b of the relay 13TER and a front contact b of the relay E3TESR in a manner to be described hereinafter.

Under normal conditions with no momentary loss of shunt occurring as a train passes through the crossing track sections, the relay 13TPSR will pick up its contacts when the train leaves the crossing track sections as follows. Clearing of the track sections 1T, AlT, ST, and A31 will cause the track relays for these sections to become energized, thus causing the time element relay 13TER and the thermal relay 13TESR to become energized.

The pickup circuit for relay 13TER may be traced from terminal B of the source through front contact a of each of the track relays lTR and 3TR, wire 31, front contact a of each of the track relays AlTR and AETR, wire 34, the winding of the time element relay Z3TER, back contact a of relay 1--3TPSR, and back contact b of relay 1--3TER to terminal C.

The pickup circuit for relay 13TESR may be traced from terminal B of the source through front contact b of each of the track relays lTR and STR, wire 32, front contact b of each of the track relays AITR and ASTR, wire 33, the winding of relay 13TESR, back contact a of relay 13TPSR, and back contact b of relay 1-3TER to terminal C.

The closing of the pickup circuit for relay 13TESR causes this relay to pick up and close its front contact b which shunts the back contact b of the time element relay 13TER. The closing of the pickup circuit for relay 13TER causes it to become energized, and after the expiration of a short time interval this relay will open its back contact b. Since contact b of relay 13TESR is already closed when this happens and since contact b of this latter relay is in multiple with back contact b of relay 13TER the energizing circuit for relays 13TESR and 1-3TER will now remain closed over front contact b of relay 13TESR. At the completion of the time period necessary for operating the front contact it of the time element relay 13TER, this contact will become closed and will complete a pickup circuit for the relay 1--3TPSR which is similar to the circuit previously traced for relay 13TER up to the winding of this relay, and thence may be traced over front contact a of relay 1-3TER, front contact a of relay 1-3TESR, and the winding of the relay 13TPSR to terminal C of the source of power.

I will now assume that while a'train is passing through the crossing track sections momentary losses of shunt are encountered, thus causing the associated track relays to momentarily become'reenergized. Under these conditions, the reenergization of the track relays for the crossing sections will complete the previously described pickup circuits for the relay ll3TESR and the time element relay 13TER. Relay 13TESR will therefore immediately close its front contacts a and b, while the relay 1-3TER will start to run its time period. At the end of each momentary loss of shunt, that is to say as soon as the train again shunts the crossing track section, the pickup circuits for the relays l-ITESR and 13TER will again become interrupted causing the relay 1-3TESR to immediately close its back contact a and open its front contact b and the thermal element of the relay 13TER to begin to cool. However, if the thermal element has been heated to any appreciable extent this relay will not immediately close its back contact b. If a second momentary loss of shunt occurs before contact b closes the picknuances w up circuits for the relays i-fiTESR and relay 1--3TER the circuit will remain open at this contact. It follows, that before energy will again be placed on the relays 1-3TESR and llfaTER it is necessary for the momentary loss of shunt to be sustained for a period long enough to allow the back contact b of the relay l3TER to reclose at the end of the cooling period and again run its full heating time period. It will be seen, therefore, that a momentary loss of shunt or successive momentary shunt losses due to undesirable rail conditions during the passage of a train through the crossing track sections will not cause the track relay repeater relay i3TPSR to become falsely energized or cause the time element relay ll-STER to reduce its time period.

Each of the approach stick relays EASE, ZASR, 3ASR, and 4ASR is controlled over time element relays and time element repeater relays in a manner similar to the above described relay ll-.' "-TPSR. A detailed description of the circuits for each of the approach stick relays is therefore not believed to be necessary.

In describing in detail the operation as a whole of the apparatus shown in the drawing, 1 shall assume that a train moves over the track Z in an eastbound direction, that is to say from left to right. The entrance of the train into section DST causes the relay D3TR to become de energized. The deenergization of this relay in turn opens at its front contacts a and b, the stick circuit for the relay 3ASR, thus causing this relay to become deenergized. With the relay SASR deenergized, a circuit is completed for energizing the routing relay RR by current of reverse polarity. This circuit passes from terminal B through front contact of relay ZASR, conductor 11, front contact d of relay lASR, conductor 18, back contact 0 of relay ZSR, conductor 64, back contact c of relay 15R, conductor 63, front contact b of relay ZRGPR, front contact b of the lock relay RLR, conductor 62, front contact a of relay ILRGPR, conductor 38, winding of the route relay RR, front contact a of relay iRGPR, conductor 43, front contact a of relay 3RGPR, back contact 0 of relay SSR, conductor 58, back contact b of relay 48R, conductor 12, back contact b of relay fiASR, conductor 2t}, and back contact a of the timing mechanism 12TE to terminal C of the source of power. The energization of relay RR with energy of reverse polarity causes the relay to move its contacts to the reverse or right-hand position, with its contact a thereby opening the circuit previously traced for relay RLR. The remaining possible energizing circuit for the relay RLR is open at contact 0! of relay 3ASR. This circuit can be traced from terminal C through front contact f of relay l-BTPSR, conductor 39, winding of relay RLR, contact a of relay RR in its right hand position, conductor 56, front contact c of relay dASR, conductor 17, to open front contact a. of relay 3ASR.

Upon deenergization of relay RLR a circuit is completed for energizing the mechanism 36 of signal 3, this circuit passing from terminal B through back contact a of relay RLR, conductor 51, back contact a of the timing mechanism 34-TE, back contact 1 of the timing mechanism 12TE, front contact g of relay ll3TPSR, conductor '71, contact 0 of relay RR closed in its right hand position, front contact a of relay ZRGPR, conductor 81, front contact .2 of relay HRGPR, conductor 82, front contact e of relay 4ASR, conductor 3!}, back contact e of relay 3ASR, conductor 28, front contact e of relay dRGPR, back contact d of relay 45R, conductor 27, signal control mechanism 36, conductor 26, contact d of the relay RR in its right hand position, and to terminal C of the source of power. The mechanism 3G of signal 3 is operated by the circuit just traced to proceed position to permit traffic movements along the track Z.

When the mechanism 3G of the signal 3 is operated to the proceed position, the relay 3RGPR becomes deenergized since the relay is energized only during a red or 6 stop aspect. Deenergization of relay 3RGPR opens its front contact a in the circuit for the signal mechanism 4G of signal 4 to insure that the signal continues to display a stop aspect.

When the train proceeds past signal 3 and into section 3T, causing the relay STR to become deenergized, the contacts a and b of relay 3TR interrupt the stick circuit for the repeater relay 1-3TPSR causing the relay to be deenergized. The deenergization of relay 1 STPSR causes its front contact g to open and interrupt the previously traced circuit for the signal mechanism 3G. The signal mechanism is thus returned to stop position. When the mechanism 3G of signal 3 reaches the stop position, the relay ERGPR will again become energized by the circuit previously traced. How ever, before relay 3RGPR opens its back contacts, relay 33R becomes energized by a circuit passing from terminal B of the source of power through back contact c of relay STR, back contact b of 3RGPR, winding of relay 38R and back contact 0 of the timing mechanism 34TE to terminal C of the source of power. Energization of relay 38R causes the relay to complete a stick circuit which is the same as the pickup circuit just traced except it includes front contact a of relay 38R instead of back contact b of relay 3RGPR.

At the same time an additional parallel stick circuit for the relay 38R is established for maintaining the relay energized in the event the relay STR becomes falsely energized due to a momentary loss of shunt. This circuit can be traced from terminal B of the source of power through back contact 0 of relay l-3TPSR, front contact b of relay 3RGPR, front contact a of relay 38R, winding of relay 35R, and back contact 0 of the timing mechanism 3-4-TE to terminal C of the source of power.

Since each of the approach stick relays lASR, ZASR, 3ASR, and dASR is protected against momentary losses of shunt due to the time delay introduced by the associated time element relay in each of the approach stick relay circuits, and since the relay 1-3TPSR (which repeats the crossing section track relays) is also protected by a time element relay, providing a momentary loss of shunt protection circuit, it can be seen that the relay 13TPSR and the approach stick relays will remain deenergized during a momentary loss of shunt. The mechanism 36 of signal 3 will also remain deenergized during a momentary loss of shunt, since the approach stick relay 3ASR interrupts its energizing circuit. With the signal mechanism 31G deenergized, the red repeater relay ERGPR will remain energized providing an uninterrupted stick circuit for the relay SSR.

As the train proceeds further along the track Z and leaves section DST the track relay DSTR becomes energized closing its front contacts a and b. It therefore can be seen, that the relay SASR wil become energized by a pickup circuit which can be traced from terminal 13 of the source of power, through front contact a of the track relay DIiTR, front contact a of the time element relay EATER (after the time element relay has run its time period) the front contact a of relay 3ATESR, and the winding of relay 3ASR to terminal C of the source of power. When relay SASR becomes energized it closes its front contact a completing a stick circuit which can be traced from terminal B of the source of power, throu h contact a of the track relay D3TR, winding of the time element relay EATER, front contact a of relay 3ASR, and winding of relay SASR to terminal C. It is noted that even though a circuit for relay SATESR is completed from the terminal B over front contact b of relay D3TR, the winding of relay SATESR, front cont-act a of 3ASR, and the winding of relay 3ASR to terminal C, the relay 3ATESR does not pick up its contacts a and b due to insufficient cur-rent passage through its winding. The current passage is only sufficient to energize the relay 3ASR to an energy level capable of causing the relay to hold its contacts up.

As the train progresses across the track intersection and into the track section A3T, the track relay ASTR becomes deenergized causing an additional interruption to the circuit of the track relay repeater relay l-3TPSR. However, since the track relay repeater relay is already deenergized, no further changes occur at this time. Further movement of the train until it clears section 3T causes the relay STR to become energized. However, since the pickup circuit for the relay l3TPSR is interrupted at contacts a and b of relay A31 R, the energization of the track relay STR has no effect on the track relay repeater relay 1-3TPSR. It is also pointed out that the opening of back contact of relay 3TR does not have any effect on the directional stick relay SSR since the directional stick relay is maintained energized over the previously traced circuit including the front contact b of relay SRGPR and the back contact 0 of ll3TPSR.

Even though the train has cleared out of the section 3T the signal 3 is maintained in its stop or red position since the circuit for the signal mechanism 3G is interrupted at the contact g of the track relay repeater relay 1-3TPSR over a circuit previously traced.

It should, therefore, be pointed out that entry of a second train into either approach track section of the track X cannot, at this time, cause either of the signals 1 or 2 to move to their clear positions, since the route relay RR and lock relay RLR are held in their previously actuated positions.

Movement of the first train into track section DAT causes the track relay D-lTR to become deenergized with the'resultant interruption of the stick circuit for the stick relay 4ASR by contacts a and b of the relay D4TR over a circuit similar to the circuit for relay IaASR, previously described. Back contact b of the relay 4ASR in its deenergized position completes a parallel stick circuit for the stick relay 38R, for maintaining the relay 38R energized upon the subsequent energization of relay l-3TPSR. This circuit can be traced from the source terminal B through back contact b of relay lASR, conductor 52, front contart b of 3RGPR, front contact a of 35R, the winding of 33R, and back contact c of the timing mechanism 3-4TE to terminal C of the source.

Further movement of the train until its clears the sections A31, causing the relay A3TR to be energized, completes a previously traced circuit for energizing the time element relay 1-3TER, and after a time period has elapsed the energizing circuit for relay l-3TPSR' becomes completed.

I shall assume. at this time that an eastbound train on track X enters the section DlT deenergizing the relay IASR through the cleenergization of relay lAR by the track relay DlTR, and the interruption of the stick circuit for relay lA-SR over the front contacts a and b of the relay EAR. Dcenergization of relay llASR causes the route relay RR to become energized with a current of normal polarity by a circuit passing from the source terminal B, over front contact c of relay 38R, front contact a of relay 3RGPR, conductor 43, front contact a of relay lRGPR, winding of relay RR, conductor 38, front contact a of relay llRGPR, conductor 62, front contact of relay RLR, now energized due to reenergization of relay l3Tl -SR, front contact b of relay ZRGPR, conductor (:3, back contact 0 of relay lSR, conductor 64, back contact 0 of relay R, conductor 18, back contact (I of relay lASR, conductor 15, and back contact a of the timing mechanism 3+4TE to source terminal C. Energization of the relay RR by current of normal polarity returns its contacts to the left hand position, thereby deenergizing the lock relay RLR. The mechanism 1G of signal ll will now be operated to its proceed position by circuit passing from source terminal B through back contact a of relay RLR, conductor 51, back contact a of the timing mechanism 3-4TE, back contact of the timing mechanism l-2TE, front Contact g of the now energized relay l-3TPSR, conductor 71, contact 0 of relay RR in its left-hand position, conductor 72, front contact d of relay SRGPR, conductor 69, front contact d of relay lRGPR, conductor 21, front contact of of relay ZASR, conductor 22, back contact e of relay IASR, conductor 23, back contact at of relay 25R, front contact 0 of relay ZRGPR, conductor 24, signal mechanism 16, conductor 25, and contact 0? of relay RR in its left-hand position to terminal C of the source of power.

The operation of the apparatus as the'train proceeds toward the track intersection on track X while a train is receding in the section D41 of track Z, is similar to that previously described while a train was traversing track 2.

It should be pointed out, however, that should the receding train still be within the track section A3T, that the clearing of signal 1 through the movement of the signal mechanism 1G could not be accomplished since the relay l-ETPSR would be deenergized at that time and thus would interrupt the energizing circuit for the signal mechanism 16.

I shall now assume that all parts of the apparatus are again in normal condition (as shown in the drawings) and that again an eastbound train on track Z enters the section A3T causing the mechanism of signal 3 to be operated to proceed position, as previously described, but that a train on track X now enters section AlT and it is desired that the train on track X shall proceed over the intersection before the train on track Z. A trainman will, therefore, operate the time element mechanism 1-2TE, thereby opening the back contact f of this time element device in the circuit traced for the mechanism 36 of signal 3, causing the mechanism 3G of signal 3 to be returned to its stop position.

After the timing mechanism 1--2TE has been fully wound up and is returning to normal position e of the timing mechanism l-2TE will close for a brief period (as explained hereinbefore) completing the circuit for energizing relay RLR, passing from source terminal B through contact e of the timing mechanism 12TE, conductor 41, winding of relay RLR, conductor 39, and contact 1 of relay 13TPSR to terminal C of the source. at the same time, a circuit will be completed for energizing the relay RR by current of normal polarity, this circuit passing from source terminal B through contact b of the timing mechanism l-ZTE, conductor 20, back contact b of relay SASR, conductor 12, back contact b of relay 48R, conductor 58, back contact 0 of relay 35R, front contact a of relay 3RGPR, conductor 43, front contact a of relay 4RGPR, relay winding RR, conductor 3%, front contact a of relay lRGPR, conductor 62, front contact b of relay RLR, front contact b of relay ZRGPR, conductor 63, back contact 0 of relay lSR, conductor 64-, back contact c of relay ZSR, conductor 18, back contact if of relay lASR, conductor 15, and contact a of 34TE the timing mechanism to terminal C of the source of power.

As soon as the timing mechanism l-ZTE reaches the normal position its contact e will open thereby deenergrzing relay RLR since the circuit first traced for relay RLR is already open at contact b of relay lASR. With relays RLR and lASR now deenergized, the mechanism 16 of signal 1 will be operated to proceed position by the circuit previously traced.

I shall new again assume that all parts are in the normal condition and that an eastbound train on track Z enters DST and that an eastbound train on track X enters section DlT. I shall further assume that after signal 3 has cleared, a loss of shunt occurs in section D3T while it is occupiedby the train on track Z, so that relay DSTR becomes falsely energized. Relay 3ASR cannot, however, become energized because the time element relay SATER maintains the pickup circuit for the relay 3ASR open. A circuit will, however, be completed for energizing the time element thermal relay 3ATER. This circuit passes 9 from source terminal B over front contact a of track relay DSTR, the winding of time element relay 3ATER, back contact a of 3ASR, and back contact b of relay SATER in parallel with the front contact b of the now energized relay BATESR, to the terminal C of the source of power.

If the loss of shunt in section D3T continues long enough or if the train on track Z backs otf of section D3'T, contact a of the time element relay 3ATER will become closed after a lapse of a measured period of time, thereby completing a pickup circuit for relay 3ASR as previously described. This will allow the signal 3 to return to stop position and the signal 1 to clear, in the normal manner previously explained, allowing passage of the train on track X.

'If, however, the loss of shunt is of sufliciently short duration so as to prevent the time element relay 3ATER from completing its time period operation, relay 3ASR will remain deenergized.

It should be pointed out at this time that it is necessary for the time element or thermal relay 3ATER to run its full time period before the relay 3ASR can be energized even though a plurality of intermittent shunt losses and returns may occur, since the subsequent energization periods of relay 3ATE-R must occur over a back contact of relay 3ATER which is only closed when relay 3ATER is cold. This operation has been previously pointed out in connection with the operation of the track relay repeater stick relay 13TPSR.

-It should be clear from the previous description that the approach of a second train on one of the two intersecting tracks, the other track of which is occupied by a first train which may be experiencing a momentary loss of shunt or several momentary shunt losses, cannot cause the routing relay and route locking relays to function to change the route previously established by the first train.

1 have described a few typical examples of the operation of the apparatus embodying my invention. In view of these examples it is believed that the operation of the apparatus for other possible traific movements can be readily understood from an inspection of the drawings without tracing the operation in detail.

Although I have herein shown and described only one form of railway signaling for intersecting tracks embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention what I claim is:

1. Control apparatus for railway signaling comprising a track section, a track relay associated with said track section and normally energized during non-occupancy of said section, a track relay repeater stick relay, a thermal relay, a thermal repeater relay, first circuit means for energizing said track relay repeater stick relay over a front contact of the track relay, a front contact of the thermal relay, and a front contact of the thermal repeater relay, and means for energizing said thermal relay and said thermal repeater relay over a back contact of said thermal relay connected in parallel with a front contact of said thermal repeater relay so that said thermal relay must be energized without interruption over a full heating period before completing said first circuit means.

2. Control apparatus for railway signaling comprising a track section, a track relay associated with said track section and normally energized during non-occupancy of the section, a track relay repeater stick relay, a thermal relay, a thermal repeater relay, first circuit means for energizing said track relay repeater stick relay over a front contact of the track relay, a front contact of the thermal relay and a front contact of the thermal repeater relay, other circuit means for energizing said thermal relay and said thermal repeater relay over a back contact of said thermal relay connected in parallel with a front contact of said thermal repeater relay so that said thermal relay must be energized without interruption over a full heating period before completing said first circuit means, and signal means controlled by said track relay repeater stick relay.

3. Apparatus for the control of railway signals for intersecting tracks comprising, a route locking relay, a route selecting means for selectively preparing signal clearing means for a given one or the other of said tracks in response to a train on the corresponding track arriving at a point a given distance from the intersection if said route locking relay is energized, means for deenergizing said route locking relay and clearing said signal upon operation of said route selecting means, directional means responsive to train occupancy in said selected route for maintaining said selected route effective until said train recedes another given distance from said intersection, and protection means operative during occupancy of the given track for preventing a change in the selected route due to successive false unoccupancy indications, said protection means comprising a thermal relay and a thermal repeater relay controlled over a circuit including a back contact of said thermal relay and a front contact of said thermal repeater relay.

4. Apparatus for the control of railway signals for intersecting tracks comprising, a route locking relay, a route selecting means for selectively preparing signal clearing means for a given one or the other of said tracks in response to the occupancy of a train on the corresponding track arriving at a point a given distance from the intersection if said route locking relay is energized, means for deenergizing said route locking relay and clearing said signal upon operation of said route selecting means, directional means responsive to train occupancy in said selected route for maintaining said selected route eflective until said train recedes another given distance from said intersection, and protection means operative during occupancy for preventing a change in the selected route due to successive false unoccupancy indications, said protection means comprising a thermal relay and a thermal repeater relay controlled over a circuit including a back contact of said thermal relay connected in parallel with a front contact of said thermal repeater relay.

5. Apparatus for the control of signals comprising a pair of line wires, a source of power and a normally energized detector relay connected across said pair of line wires, means for at times deenergizing said detector relay, a detector repeater stick relay, a thermal relay, a thermal repeater relay, an energizing circuit for said detector repeater stick relay including a front contact of said detector relay, a front contact of said thermal relay and a front contact of said thermal repeater relay, a stick circuit for said detector repeater stick relay including the windings of said thermal and thermal repeater relays connected in parallel, a pickup circuit for said thermal relay including a back contact of said thermal relay and a front contact of said thermal repeater relay connected in parallel, and a back contact of said detector repeater relay, and signal means responsive to the operation of said detector repeater stick relay.

References Cited in the tile of this patent UNITED STATES PATENTS 2,148,005 Allen et al. Feb. 21, 1939 2,233,932 Allen Mar. 4, 1941 2,289,857 Allen July 14, 1942 2,366,802 Pflasterer Ian. 9, 1945 2,684,435 Haines July 20, 1954 2,760,054 Kemmerer Aug. 21, 1956 

